It isn't a mac problem. I had a simliar problem when I was trying to rotate a picture. When I went to draw...I was not able to click on "free rotate" as it was "grayed out" like yours. For some reason when I clicked on "rotate left 90" it opened up the "free rotate". I wish I could tell you what specifically to click on to open it up...but there is something there that will open it up for you.
Here were the original steps...are you doing step #5
1. Open up Microsoft Word.
2. Go to insert > WordArt > then select the style of text you prefer
3. Type your text, choose the size you want the text to be, then click OK. If you want the image/pattern to show pretty well in the text, you'll need a bold or big text like Impact, Arial Black, etc.
4. Right-click on the text > Click 'format WordArt'
5. A window should pop up, then under 'fill', click 'fill effects'
6. Click the tab that says 'picture' > select picture > choose the image/pattern you want > Click OK.
7. Then VOILA! You should have your image/pattern filled text! You can drag the sides or corners/box to change the size of the text to your liking.